cardiovascular system Flashcards
(20 cards)
definition of myogenic
it originates in muscle tissue
how does the heart beat
blood is pumped through the atria and out through the ventricles. the heart muscle is described as myogenic as the heart beats it sends an electrical signal in the sinoatrial node (SAN). this electrical signal spreads through the heart as a wave of excitation (Mexican wave)
what is a sinoatrial node (SAN)
it is a small mass found in the wall of the right atrium that generates a heartbeat (pacemaker)
what is an atrioventricular node (AVN)
relays the impulse between the upper and lower sections of the heart
how does an electrical impulse travel through the heart
- it starts at the SAN and spreads through the walls of the atria
- the impulse then passes through the AVN where it is delayed for 0.1 seconds to enable the atria to fully contract before ventricular systole begins
- the impulse then travels through the bundle of his, which the splits off to the Purkinje fibres, which spread though out the ventricles, causing them to contract (ventricular systole)
what is the sympathetic nervous system
this is where it stimulates the heart to beat faster
what is the parasympathetic system
returns the heart to its resting level
where are the cardiac control centre located
medulla oblongata
what is the medulla oblongata
the most important part of the brain as as it regulates processes that kepp us alive
what is the cardiac control centre stimulated by
chemoreceptors, baroreceptors and proprioceptors
what do the chemoreceptors do
detect an increase in CO2 => cardiac control centre => sympathetic system => SAN increases heart rate
what do the baroreceptors do
detects an increase in blood pressure => cardiac control centre => parasympathetic => SAN decreases the heart rate
what do the proprioceptors do
detect an increase in muscle movement => cardiac control centre => sympathetic system => SAN increases heart rate
what is stroke volume
volume of blood pumped out the by the heart ventricles in each contraction (average is 70ml)
what does stroke volume depend on
- venous return
- elasticity of cardiac fibres
- contractibility of cardiac tissue
what is venous return
when this increases, stroke volume will also increase
what is the result of stroke volume in response to exercise
stroke volume increases as exercise intensity increases
definition of heart rate
the number of times the heart beats per minute
what is the ejection fraction
the percentage of blood pumped out by the left ventricle per beat
what is venous return
the return of blood to the right side of the heart via the vena cava
